Pfizer’s Accord for a Healthier World program is a comprehensive initiative aimed at addressing healthcare disparities by providing the company’s full portfolio of medicines and vaccines on a not-for-profit basis to 45 lower-income countries. However, many of these countries are located near the equator with extreme tropical climates, posing a challenge for the stability testing of medicines and vaccines. The International Council for Harmonisation (ICH) has designated five stability zones, with Zone IVa and Zone IVb presenting the greatest challenges due to high heat and humidity conditions.
Pfizer’s scientists have developed a novel statistical approach to estimate shelf life in Zone IV markets without the need for new long-term studies. This approach leverages existing long-term data from Zone II conditions and short-term accelerated data to provide a scientifically sound estimation of shelf life. The World Health Organization’s (WHO) stability guidance allows for alternative approaches if they are scientifically justified, providing flexibility for initiatives like the Accord.
The approach uses the Arrhenius model to interpolate the expiry at Zone IV conditions, taking into consideration all stability-limiting attributes for each product and the probability of breaching specified limits. The model has been applied to two product examples, which will be presented at the International Society for Pharmaceutical Engineering’s 2025 ISPE Annual Meeting & Expo.
The development of this novel approach is crucial for increasing access to quality medicines and vaccines in lower-income countries. By estimating shelf life in Zone IV markets, Pfizer can ensure that its products are safe and effective for use in these regions. The company hopes to engage with regulatory agencies and receive feedback from peers to further validate the model.
The ultimate goal is to apply this model more broadly, beyond Pfizer’s portfolio, to save on sample and testing resources. This could have a significant impact on global health equity, as many lower-income countries struggle to access quality medicines and vaccines due to lack of stability testing. By sharing this approach, Pfizer aims to contribute to the development of more effective and sustainable healthcare systems in these regions.
The Accord for a Healthier World program is a significant step towards addressing healthcare disparities, and the development of this novel statistical approach is a crucial component of this initiative. By providing access to quality medicines and vaccines, Pfizer is helping to close the health equity gap and ensure that people in lower-income countries have access to the same level of healthcare as those in higher-income countries.